The present invention relates to a pressure sensor, and more specifically, to a pressure sensor comprising a housing storing a pressure sensing element and a connector case, that can be assembled easily with reduced number of assembly steps.
Japanese Laid-Open Provisional Publication No. 11-351990 discloses an absolute pressure type pressure sensor or a sealed gauge pressure type pressure sensor for detecting fluid pressure. The disclosed pressure sensor comprises a metal housing having an inner chamber communicated to a pressure sensing chamber and a thin wall rising portion at the upper end of the housing; a metal cylindrical pressure case having an inner chamber, a separation wall that divides the inner chamber into upper and lower space and a thin wall rising portion at the upper end of the case; and a connector case made of an insulating material; the housing, the pressure case and the connector case stacked with each rising portion caulked to form an integrated inner space for storing a sensor element for detecting pressure and an electric circuit, the pressure case further equipped with a penetrating condenser.
Further, the present applicant has filed an application (Japanese Patent Application No. 11-312611) related to a pressure sensor, the object of which is to reduce the influence of electromagnetic noise that may affect the output voltage of the pressure sensor. The disclosed pressure sensor comprises a housing having a pressure introduction hole, a sensor element composed of a semiconductor element having piezoresistance effect, a holder for fixing the sensor element, and a pressure case, wherein the sensor element, the holder and the pressure case are welded together as pressure sensor body in an airtight manner so as to create a reference pressure chamber, the pressure sensor body disposed within the housing in an insulated manner.
According to the above-mentioned invention, it is possible to reduce the influence of electromagnetic noise acting on the pressure sensor, but since the structure around the area where the pressure sensor body and the connector come into contact is complex, many steps are required to assemble the pressure sensor and the cost of manufacturing the sensor cannot be cut down.
The present invention is aimed at providing a pressure sensor that overcomes the prior art problems, with a simplified structure for connecting the pressure sensor body and the connector, requiring reduced number of assembly steps.
In order to achieve such object, the present pressure sensor comprises a housing having a pressure introduction hole, a pressure sensing element composed of a semiconductor element having piezoresistance effect, a holder to which the pressure sensing element is fixed, a connector case, a pressure sensor body creating a reference pressure chamber with the pressure sensing element and the holder bonded in an airtight manner, a circuit board having electrode pads mounted on the holder of the pressure sensor body, and electrically conductive spring bodies having elasticity for connecting connectors fixed to the connector case to the electrode pads.
According further to the present invention, one end of each spring body for connecting the connector to the electrode pad is fixed to the lower end of each connector, the other end being bent downward and the tip of the end forming a curved portion.
According further to the present invention, the area of the spring body from the portion fixed to the lower end of the connector to the area being bent downward is supported by the bottom portion of the inner chamber of the connector case.
According to the present invention, the pressure sensor is a gauge pressure type pressure sensor, but the reference pressure chamber can also be formed in an airtight manner using a pressure case, and the pressure sensor can be either an absolute pressure type or a sealed gauge pressure type pressure sensor.
According to another aspect of the present invention, the pressure sensor comprises a housing having a pressure introduction hole, a pressure sensing element composed of a semiconductor element having piezoresistance effect, a holder to which the pressure sensing element is fixed, a connector case, a pressure sensor body creating a reference pressure chamber with the pressure sensing element and the holder bonded in an airtight manner, a circuit board having electrode pads mounted on the holder of the pressure sensor body, electrically conductive spring bodies having elasticity for connecting connectors fixed to the connector case to the electrode pads, and a seal member mounted between the pressure sensing element and the housing, the size of the seal member determined so as to adjust the load received by the pressure sensing element.
According further to the present invention, the pressure sensor comprises a guide member having an opening formed to the center thereof mounted between the housing and the holder, the seal member disposed within the opening of the guide member.
According to the pressure sensor of the present invention having the characteristics mentioned above, a seal member is equipped between the pressure sensing element and the housing. Therefore, by adjusting the size of the seal member, the amount of fluid passing through the seal member from the housing toward the pressure sensing element can be controlled, and thereby, the increase of load received by the pressure sensing element can be effectively suppressed.